netdev - [bpf PATCH] net: tcp_bpf, correctly handle DONT

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Date:   Mon, 13 May 2019 21:42:03 -0700
From:   John Fastabend <john.fastabend@...il.com>
To:     ast@...nel.org, daniel@...earbox.net
Cc:     netdev@...r.kernel.org, bpf@...r.kernel.org,
        john.fastabend@...il.com
Subject: [bpf PATCH] net: tcp_bpf,
 correctly handle DONT_WAIT flags and timeo == 0

The tcp_bpf_wait_data() routine needs to check timeo != 0 before
calling sk_wait_event() otherwise we may see unexpected stalls
on receiver.

Arika did all the leg work here I just formaatted, posted and ran
a few tests.

Fixes: 604326b41a6fb ("bpf, sockmap: convert to generic sk_msg interface")
Reported-by: Arika Chen <eaglesora@...il.com>
Suggested-by: Arika Chen <eaglesora@...il.com>
Signed-off-by: John Fastabend <john.fastabend@...il.com>
---
 net/ipv4/tcp_bpf.c |    5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/net/ipv4/tcp_bpf.c b/net/ipv4/tcp_bpf.c
index 1bb7321a256d..27206b2064db 100644
--- a/net/ipv4/tcp_bpf.c
+++ b/net/ipv4/tcp_bpf.c
@@ -27,7 +27,10 @@ static int tcp_bpf_wait_data(struct sock *sk, struct sk_psock *psock,
 			     int flags, long timeo, int *err)
 {
 	DEFINE_WAIT_FUNC(wait, woken_wake_function);
-	int ret;
+	int ret = 0;
+
+	if (!timeo)
+		return ret;
 
 	add_wait_queue(sk_sleep(sk), &wait);
 	sk_set_bit(SOCKWQ_ASYNC_WAITDATA, sk);